Ibn Majah

Hadith Commentary:
➊
Although the word "unjustly" (na-haqq) does not appear in this hadith, the requirements of the Shari'ah dictate that what is meant here is unlawful killing. However, in some narrations, the explicit mention of "without right" is present. Furthermore, it is stated in Sunan an-Nasa'i:
"Whoever kills a dhimmi (non-Muslim under Muslim protection) unjustly, Paradise is forbidden for him."
(Sunan an-Nasa'i, al-Qasamah, Hadith: 4752)
➋
Such a person will not even smell the fragrance of Paradise until he receives the punishment for his crime, or it refers to the one who killed a dhimmi considering it lawful and permissible.
In any case, this hadith is to be understood as carrying a severe warning.

Hadith Commentary:

This includes all those disbelievers who have been granted protection (aman) in the abode of Islam (dar al-Islam), whether by the Islamic ruler on the basis of jizya (tribute) or a peace treaty, or if any Muslim has granted them protection. However, if this is not the case, then according to Islamic law (shar‘ of Islam), it is permissible to take the life of such a disbeliever or seize his wealth.

For example, those disbelievers who live outside the abode of Islam, on the frontier, it is lawful (halal) to go into their territory and plunder or kill them or their disbelieving subjects.

In the narration of Isma‘ili, it is stated that the fragrance of Paradise (jannah) is perceived from a distance of seventy years’ journey, and in one narration of Tabarani, one hundred years is mentioned.

In another narration, five hundred years, and in the narration of Firdaws of Daylami, one thousand years is mentioned. There is no contradiction in this, because if the fragrance of Paradise is perceived from a distance of one thousand years’ journey, then from five hundred, one hundred, seventy, or forty years’ journey, it will be perceived even more strongly.

Hadith Commentary:
(1)
By "mu'ahid" is meant that non-Muslim whose protection is the responsibility of the Muslims, i.e., he is a citizen of the Islamic state, whether he has been granted safety by the head of state in exchange for jizyah or through a peace treaty, or whether any Muslim has granted him asylum. In all these cases, it is not permissible to kill any disbeliever unjustly. (Fath al-Bari: 12/323)

(2)
If any non-Muslim, while residing in the Islamic state, engages in aggressive actions, it is the duty of the government to take notice of it. Similarly, if disbelievers at the borders of the Islamic country are engaged in rebellious activities or are causing harm to the lives and property of Muslims, then preventing them is also the foremost duty of the Islamic government. The Muslim subjects should not take the law into their own hands or carry out any kind of action themselves.

(3)
Hafiz Ibn Hajar rahimahullah has written, quoting from Muhallab, that if a Muslim kills a dhimmi or a mu'ahid, then the Muslim will not be killed in retribution (qisas), because in this hadith only the warning of punishment in the Hereafter has been mentioned for his killing; there is no mention of a worldly punishment in it. (Fath al-Bari: 12/234) We will discuss this matter in detail at another time, insha Allah ta'ala.

Urdu marginal note:
"Forty years"—the mention of forty years does not negate seventy, therefore this narration is not contrary to the previous narration. And if the meaning of abundance is intended, then there is absolutely no problem at all. The purpose is that he will remain very far from Paradise. However, what is meant is the beginning; otherwise, in the end, every believer will enter Paradise, as has already been mentioned earlier.

Takhrij:
«أخرجه البخاري، الجزية والموادعة، باب إثم من قتل معاهدًا بغير جرم، حديث:3166.»©Explanation:
This hadith proves that it is forbidden (haram) to kill any dhimmi (non-Muslim under Muslim protection) or mu'ahid (one with whom there is a covenant) without cause or without any legitimate Islamic right. However, such a Muslim murderer is not subjected to retribution (qisas) in this world; therefore, his punishment in the Hereafter has been mentioned.